Cork Gaskets or RTV Silicone for MKV?


Currently I have the Oil Pan and Side/Tappet Cover off of my 3.5 MK V.
I have cork replacement gaskets for both but was considering using a silicone product as a sealant when reinstalling both items.

Any feedback regarding anyone’s experiences or the best way forward would be greatly appreciated.

Regards Frank

Hello Frank,

My MKV was recently fitted with a good quality cork gasket without a sealant. It’s been leak free for 500 miles. I guess you have to think about trying to remove a gasket which has been sealed on as it will most likely break. Just don’t over-tighten the gasket.


I usually clean one surface, apply a thin coat of silicone and place the gasket over and assemble the unit. It’s a way of keeping the gasket in the proper place when assembling things.

I imagine there are different opinions about gasketing; cork, paper, rubber, cardboard, tube sealant alone…
I don’t often find cork gaskets, but when I have used them I put tube sealant on one surface only, so it can be disassembled with likelihood that the gasket will remain in one piece. It worked with my Mark V rocker cover recently, having been on there about 5 years.
My favorite brand in the USA is Permatex No. 2, though I suppose there are other brands with similar characteristics around the world.

Thanks so much for your insights everyone.
I was considering ditching the cork and using an RTV Silicone gasket maker only.
I have used such a product before in place of cork or paper gaskets and they seem to work well. Only problem can be disassembling parts again later in time if required as the silicone achieves a very strong bond.
I think I will go ahead with the cork and a bit of sealant on this occasion.
Tim your gasket looks the same in appearance as mine. Did you score it from Jag1 in Noble Park?

Yes, Frank, I think that was the place?



I would never put any silicone anywhere near my MKV engine (ok, it’s actually a MK IV engine, but nevertheless).

Sorry for some lost time, I was away so long I had forgotten my password etc.
I hope people can keep their political view and all harassment out of Jag-Lovers.

I am slowly starting to put the engine back together, I only got the block back, resleeved, in early June and have tons of other stuff to take care of.

It’s actually engine number SL2199 and not SL2194 like I had thought for over a decade.

If silicone gets loos inside the engine it creates oil blockages immediately.
I use Blue Hylomar on the paper gaskets and also on the head gasket (Composite) very thinly applied. Never had any trouble with it, and usually the gaskets come out nicely in one piece when disassembled.


Pekka T. -647194-

Hello Pekka, your details and insights as you progress with the engine work will be appreciated very much. Cheers and stay well!

Agree, I never found RTV silicone to work very well with sealing oil, having tried it once on a gearbox, although it is fine for sealing water, like in your bathroom and kitchen.
I once used it in an emergency on a carb float, and in gasoline it lasted about 20 miles, just enough to get me home. :grin:

Let me revise my statement. I was thinking of the general use RTV silicones found in home repair centers.
I see that the Permatex Optimum Black and Optimum Grey automotive gasket maker sealants which I do use are actually called silicone on their Tech Data Sheets.

Hi Frank,

I found out that you can buy them through the Jag Club in Queensland.
Contact Fred Richardson if you wish to purchase any of the following parts which the club has for sale:
Sump gaskets & rocker cover gaskets for Mk4/5, 2.5/3.5litre. $25 for sump and $15 for rocker cover.
Sets of 4 gaskets for each side of spacer block between carbs and head on Mk4/5. $8 per set.
Exhaust gaskets, pipe to manifold, (square ones), Mk4/5 & XK120/140; $9 set of 2.
Exhaust gaskets head to manifold, 3.5 litre, Mk4/5, $15 per set.


Cheers Tim

Thanks for the contact details. Will come very handy.

Much appreciated

Silicone, misused or badly applied, can be a mess.

Done properly, it works fine, and I speak from over 50 years of using it.

It most definitely is NOT gasoline-resistant.

Permatex makes a fuel resistant sealant called Permashield 85420. I use it on SU fuel pumps. But they call it polyester urethane, not silicone.

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I sent an email to the above address but never heard back. Just wondering if it is the correct address.


That was the one in their magazine. I simply copied and pasted the section directly. He might be away?